ESTRO 2025 - Abstract Book

S1713

Clinical - Sarcoma & skin cancer & malignant melanoma

ESTRO 2025

Material/Methods: Medical records of 50 patients with non-metastatic retroperitoneal sarcoma between 2009 and 2022 in a single institution were analysed. Results: The median-age of patients was 50.5 years (IQR: 39–59), with a male predominance (58%). The most common symptom was abdominal pain (56%) and liposarcoma (48%) was the predominant histology, followed by leiomyosarcoma (40%). The mean tumor size was 12 cm (range: 3–43 cm). Surgery followed by PORT(70%) was the most common treatment sequence. Surgery was performed in 96% of patients, with 47.9% undergoing simple resection, 43.8% compartment resection. R0 resection was achieved in 68.8% of cases. Neoadjuvant chemotherapy was administered to 20%, postoperative radiotherapy (PORT) to 96%, definitive radiotherapy to 4%, and adjuvant chemotherapy to 10%. The median radiotherapy dose for PORT was 50.4 Gy (IQR: 50.4–54.4 Gy), with definitive radiotherapy dose 60 Gy. Conformal radiotherapy technique was used. At a median follow-up of 46 months, 14% of patients were disease-free, 70% had active disease, and 16% had died. The 5-year local control (LC), progression-free survival (PFS), and overall survival (OS) rates were 53.1%, 31.6%, and 50%, respectively. LC was higher in patients with tumors ≤10 cm (72% vs. 48.4%), low-grade tumors compared to high-grade (55.6% vs. 51.4%), and R0 resection compared to R+ resection (55.3% vs. 48.2%). PFS was better in patients with tumors ≤10 cm (43.4% vs. 29.1%), liposarcoma compared to leiomyosarcoma (46.1% vs. 17.1%), low-grade compared to high-grade tumors (44% vs. 27.6%), and R0 versus R+ resection (35.8% vs. 21.4%). OS was superior in liposarcoma compared to leiomyosarcoma (78.3% vs. 21.1%) low-grade compared to high-grade tumors (78.8% vs. 42.8%) and slightly higher in R0 compared to R+ resection (50.5% vs. 50.3%). Acute toxicities included grade 1 dermatitis (46%) and grade 2 enteritis/nausea (1% each), while late toxicities included bowel stricture in 4% of cases. Local recurrence(LR) occurred in 38%, distant in 28%, and combined local and distant in 6%. Seventy-three percent of LR were infield. Among relapsed patients, 41% underwent salvage surgery, 36% received supportive care, 14% had palliative chemotherapy, and 9% received palliative radiotherapy. Five-year LC after surgical salvage was 38.5%. Conclusion: Tumor histology, grade, and surgical margins affect outcomes, highlighting the need for treatment intensification, such as radiotherapy dose escalation and proton therapy, as most local recurrences occur within the treatment field.

Keywords: Retroperitoneal sarcoma, PORT, Liposarcoma

3619

Digital Poster Efficacy and Recurrence of Superficial Radiotherapy in Basal Cell Carcinoma: A Retrospective Analysis of Dose and Long-Term Outcomes Ana Galán García, Arantxa Campos Bonel, Claudia Colom Pla, Claudia Laborda Díaz, María Cerrolaza Pascual, Cristina García Aguilera, Irene Carruesco Crespo, Blanca García Gimeno, Sergio A Lozares Cordero, Reyes Ibáñez Carreras, Martín Tejedor Gutiérrez Oncología Radioterápica, Hospital Universitario Miguel Servet, Zaragoza, Spain Purpose/Objective: Basal cell carcinoma (BCC) is the most common skin cancer, predominantly affecting sun-exposed areas such as the nose and temple. While surgical excision is the standard treatment, superficial radiotherapy (RT) represents a well established alternative for elderly patients, those with comorbidities, or lesions in challenging anatomical locations. Despite its advantages in preserving surrounding tissues and providing excellent cosmetic outcomes, factors